Electrode system for trochotrons



Jan.'2, 1951 N. E. G. BACKMARK ETAL 2,536,150

ELECTRODE SYSTEM FOR TROCHOTRONS Filed July 18, 1949 Patented Jan. 2, 1951 UNITED STATES PATENT OFFICE ELECTRODE SYSTEM FOR TROCHOTRONS Sweden Application July 18, 1949, Serial No. 105,406 In Sweden July 19, 1948 8 Claims.

This invention relates to embodiments of electrodes in tubes of the type described in United States patent application of Alfven and Romanus, Serial No. 651,920, filed March 4, 1946, which issued as Patent Number 2,513,260 on June 27, 1950, and which are called trochotrons. Such tubes contain a plurality of electrodes intended to receive or control, or both receive and control an electron current, the particular electrons of which are moving in a magnetic field in trochoidal paths. Two adjacent electrodes of the mentioned kind may at suitable choice of the electrode voltage be hit each by itself or together by the electron beam, the path of which within the tube is determined by the present electric and magnetic fields. The trochoidal movement of the particular electron consists of a translatory component and a circular movement superimposed thereon. In case of a homogeneous magnetic field the translatory movement will approximately follow an equipotential line through the tube and the radius of the circular component is a function of the strength of the electric and the magnetic field.

When the beam hits one or more electrodes some of its electrons have a tendency to pass out through the spacings between the electrode touched by the beam and the adjacent electrodes due to the dispersion of the beam caused by the mentioned circular movement. These scattered electrons cannot be directly controlled "through the impressed fields and give birth to disturbing leak currents in those electrodes of the tube, which are not to be hit by the beam.

Such leakages can be avoided by arranging mica plates behind the electrodes as seen from the electron path, so that no openings between the electrodes are obtained. The leakage can certainly be reduced in this way but the mica plates receive uncontrollable and unstable chargings through electrons impinging on the plates, which disturbs the function of the tube. One of the adjacent electrodes is in the present invention preferably provided with a small edge bent along the other electrode at a certain distance from the same whereby the influence from said chargings is reduced and the field between the electrodes is made more easily controllable on that side of the electrodes, where the beam is.

The present invention relates to embodiments of adjacent electrodes, through which leak currents between the electrodes are prevented without such disturbing influences arising.

According to the invention two adjacent electrodes, which may be hit each by itself or simultaneously by the electron beam, are so shaped that a slit is formed between the parts of the adjacent electrodes lying close to each other, said slit having a length perpendicular to the magnetic field that is at least as great as the minimum distance between the electrodes.

In the following the invention will be described by way of example with reference to the accompanying drawing, which shows different embodiments of electrodes. Fig. 1 shows an embodiment of electrodes with a single slit between the electrodes, Fig. 2 an embodiment with a slit prolonged in angle and being especially suitable to prevent the scattering of secondary electrons. possibly released at the electrodes, Fig. 3 shows a labyrinthine embodiment of the slit betwee the electrodes suitable for the same purpose, Fig. 4 a modification of the embodiment according to the Figures 1 and 2 and Fig. 5 an electrode device, where the electron beam is completely caught because the contact electrode is performed as a V-shaped channel forming a pointed angle with adjacent electrodes.

Fig. 1 shows diagrammatically a trochotron consisting of a glass envelope I, an electron source consisting of a cathode 2 and an anode 3 and a number of electrodes intended to receive the electron current. These electrodes are suitably arranged in such a way that they form open bottom boxes the tops of which consist of electrodes 4'44" etc., the so-called contact electrodes and the sides of which are formed by electrodes, so-called spades 5'5"5 etc., arranged mainly perpendicularly to the contact electrodes. Between these electrodes and an electrode rail 6 that electric field is formed which determines the path of the trochoidal beam 8 through the tube together with a magnetic field indicated in the figure through the arrows 1' running perpendicularly to the longitudinal direction of the tube and parallelly with the plane of the indicated electrodes. In the figure the field distribution is supposed to be such that the beam hits the spade 5 as well as the contact electrode 4".

The electrodes 4' 4" etc. are at their edges adjacent to the electrodes 5 and 5 etc., respectively, provided with a lap or flange 9 so performed that a slit arises between the electrodes, the width of which is indicated by b and the length or depth of which perpendicular to the magnetic field and parallel with the adjoining ed es is indicated by I.

For those fields which are suitable for operation of the tube and which give the electron path the shape of an extended cycloid, practically all the electrons appearing in the vicinity of a slit, will b caught either by one or the other of the adjacent electrodes if the length or depth of the slit l is made greater than the width b of the same, based on the condition that the radius of the circular component of the electron movement is greater than half the width b of the slit. This radius can however by means of the magnetic field always be made so great that this condition is fulfilled. With regard to the size of the boxes formed by a pair of spades and. an intermediate contact electrode 4, in which boxes the electron beam has to come to be able to hit the contact electrode or some other electrode not indicated here, without being disturbed by the spades, it is not suitable to choose the radius of the circular movement too great and thus not the width of the slit too great either. In tubes of the kind indicated in the figure a good result may be achieved, if the slit is only performed with a minimum width b, which is less than of the distance between two adjacent spades.

The Figures 2 and 3 show other embodiments giving further safety as to the avoidance of stray electrons, especially with regard to secondary electrons, which may be'released at the electrodes when these are hit by the electron beam. By a labyrinthine shape of the spacing between adjacent electrodes great assurance is obtained thatv all primary and secondary electrons will be caught by one of the electrodes.

In the Figures 4 and 5 other embodiments according to the invention are shown. According to Fig. 4 the contact electrodes are performed with a rather great radius of curvature in the part between the flange 9 and the remaining part of the electrodes 4', 4" etc. According to Fig. 5 the electrodes 4 are channel shaped and form a pointed angle with an adjacent electrode. Practically all the electrons coming into a box, are caught by one of those electrodes which form a pointed angle with one another, provided that the width b indicated in the figure is less than (1/4.

In the figures only some embodiments are shown of all the ones which may be supposed to fall within the scope of the invention.

We claim:

1. An electrode system for trochotrons comprising in combination, a plurality of receiving electrodes for the trochoidal electron beam, each two adjacent electrodes subject individually or jointly to being struck by the electron beam being separated by a slit between parts of the electrodes lying close to each other, each of said electrodes bordering said slit having a portion thereof directed generally in the direction of the depth of the slit and perpendicular to the magnetic field, said portion being of such dimension and the electrode spacing being such that the depth of the slit is at least as great as its width.

2. An electrode system for trochotrons comprising in combination, a plurality of sequentially arranged and spaced receiving electrodes for the trochoidal electron beam, each two adjacent electrodes subject individually or jointly to being struck by the electron beam being separated by a slit of substantially uniform Width throughout its length between parts of the electrodes lying close to each other, each of said electrodes bordering said slit having a portion thereof directed generally in the direction of the depth of the slit and perpendicular to the magnetic field, said portion being of such dimension and the electrode spacing being such that the depth of the slit is at least as great as its width.

3. The electrode system as defined in claim 1 wherein the said portions of said electrodes adjacent certain of said slits are provided with flanges to form the slit into a labyrinthine shape.

4. The electrode system as defined in claim 3 wherein the labyrinthine slits are formed at one side only of each electrode Whose general plane parallels that of the magnetic field and the main path of the electron beam, said side being most remote from the source of the beam.

5. The electrode system according to claim 1 wherein the adjacent electrodes converge at an angle with each other to form the said slit.

6. The electrode system as defined in claim 1 in which adjacent electrodes have the general plane of their major area substantially at right angles to each other, the electrodes having these areas substantially parallel to the general paths of the beam having side flanges paralleling the remaining electrodes and providing the slit depth.

'7. The electrode system of claim 6 in which said flanges extend away from said plane and beam and merge with said electrode area on a relatively large radius of curvature.

8. The electrode system of claim 1 in which the alternate electrodes have their plane substantially normal to the general path of the beam, the remaining electrodes being of V shape with the apex directed toward the beam.

NILS ERIK GUSTAV BACKMARK. KARL EVERT INGEMAR JANSSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,293,567 Skellett Aug. 18, 1942 2,414,121 Pierce Jan. 14, 1947 OTHER REFERENCES Article by H. Alfven and H. Romanus in Nature of November 1, 1947, vol. 160, No. 4070. 

